1. Field of the Invention
This invention relates to vascular access monitoring, in particular it relates to a device and method for monitoring for the presence of a needle or cannular to determine if it becomes dislodged from a patient.
2. State of the Art
In a number of medical treatment regimes it is necessary to have access to the vascular system through a skin piercing, for example in drug infusion or blood processing treatments like dialysis.
It can be very important to know if a needle becomes dislodged from a patient, and in some cases a dislodged needle can cause serious medical consequences, for example dislodgement of a needle providing life supporting drugs, if not detected could even result in death, as could dislodgement of a blood return needle in a hemodialysis treatment whereby the dialyser can pull blood from the body but not return it. This is especially dangerous in overnight dialysis while the patent is asleep as they would not see the blood escaping.
Several devices have been proposed for detecting if a needle becomes dislodged from a patient, for example in hemodialysis sensors have been used which look at the effect of the presence of a needle on an electric circuit, for example as described in US2005/0038325. Another known device is described in DE 198 02 985 which discloses the use of an optical reflected signal to detect if the needle has become dislodged. The needle has a reflector mounted thereon to reflect an infra red signal from a transmitter back to a receiver. In this device the adaptation of the needle is required which is highly undesirable as it requires a change to a cheap part which is an accepted standard part across the industry.